The effects of clothing layers on the thermoregulatory responses to short duration babywearing in babies under 12 months old.

Carrying babies in a sling, that is, babywearing, is a popular practice among new parents. Babies are thermally vulnerable and public health bodies advise to dress them in one extra layer than the adult. However, these guidelines do not consider babywearing and it is unclear whether babies' clothing insulation should be modified during babywearing. Here we quantified the effects of babies' clothing layers on the thermoregulatory responses to short duration babywearing in babies under 12 months old. Nine babies (4F/5M; 7.3 ± 3.1 months; 9 ± 2.5 kg) and 9 mothers (34 ± 3.0 years) performed two trials in a thermoneutral environment (23°C; 50%RH). During trials, babies wore either 1 (sleepsuit) or 2 (vest + sleepsuit) clothing layers, and mothers performed 15-min stepping exercise while babywearing. We recorded mothers and babies' tympanic temperature (Tty ), babies' local skin temperatures (Tsk ; on the carotid artery area, arm, abdomen, lower back, and thigh), and mothers' perception of babies' thermal state. Babies' Tty did not change after 15-min babywearing (mean change: -0.13°C [-0.30, +0.05]; p = .141), in either clothing trial (difference between trials: +0.05°C [-0.15, +0.25]; p = .591). On the contrary, local Tskin increased across all sites tested (mean increase = +0.71°C [+0.41, +1.01]; p = .038) and similarly between clothing trials, with the abdomen showing the largest change (+1.10°C [+0.32, +1.85]). Mothers did not perceive any change in babies' thermal state. We show that 15-min babywearing increase babies' skin, but not tympanic, temperature by up to 1.1°C on certain body regions, and that this effect is not exacerbated by adding 1 layer of light clothing to the baby.